package org.simantics.acorn;

import java.io.IOException;
import java.math.BigInteger;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicBoolean;

import org.simantics.acorn.cluster.ClusterImpl;
import org.simantics.acorn.exception.AcornAccessVerificationException;
import org.simantics.acorn.exception.IllegalAcornStateException;
import org.simantics.acorn.exception.InvalidHeadStateException;
import org.simantics.acorn.internal.ClusterSupport2;
import org.simantics.acorn.lru.ChangeSetInfo;
import org.simantics.acorn.lru.ClusterInfo;
import org.simantics.acorn.lru.ClusterLRU;
import org.simantics.acorn.lru.ClusterStreamChunk;
import org.simantics.acorn.lru.FileInfo;
import org.simantics.acorn.lru.LRU;
import org.simantics.db.ClusterCreator;
import org.simantics.db.Database.Session.ClusterIds;
import org.simantics.db.Database.Session.ResourceSegment;
import org.simantics.db.ServiceLocator;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.impl.ClusterBase;
import org.simantics.db.impl.ClusterI;
import org.simantics.db.impl.ClusterSupport;
import org.simantics.db.procore.cluster.ClusterTraits;
import org.simantics.db.service.ClusterSetsSupport;
import org.simantics.db.service.ClusterUID;
import org.simantics.utils.FileUtils;
import org.simantics.utils.threads.logger.ITask;
import org.simantics.utils.threads.logger.ThreadLogger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ClusterManager {
    
    final static Logger LOGGER = LoggerFactory.getLogger(ClusterManager.class); 

	private ArrayList<String> currentChanges = new ArrayList<String>();

	public final Path dbFolder;
	public Path lastSessionDirectory;
	public Path workingDirectory;

	public LRU<String, ClusterStreamChunk> streamLRU;
	public LRU<Long, ChangeSetInfo> csLRU;
	public ClusterLRU clusterLRU;
	public LRU<String, FileInfo> fileLRU;

	public MainState mainState;
	public HeadState state;

	private long lastSnapshot = System.nanoTime();

	final public ClusterSupport2 support = new ClusterSupport2(this);

	/*
	 * Public interface
	 * 
	 */

	public ClusterManager(Path dbFolder) {
		this.dbFolder = dbFolder;
	}

	public ArrayList<String> getChanges(long changeSetId) throws AcornAccessVerificationException, IllegalAcornStateException {
		ChangeSetInfo info = csLRU.getWithoutMutex(changeSetId);
		info.acquireMutex();
		try {
			info.makeResident();
			return info.getCCSIds();
		} finally {
			info.releaseMutex();
		}
	}

	public ClusterBase getClusterByClusterKey(int clusterKey) throws DatabaseException, AcornAccessVerificationException, IllegalAcornStateException {
		return clusterLRU.getClusterByClusterKey(clusterKey);
	}
	
	public ClusterBase getClusterByClusterUIDOrMake(ClusterUID clusterUID) throws DatabaseException, AcornAccessVerificationException, IllegalAcornStateException {
		return clusterLRU.getClusterByClusterUIDOrMake(clusterUID);
	}

	public ClusterImpl getClusterByClusterUIDOrMakeProxy(ClusterUID clusterUID) throws DatabaseException, AcornAccessVerificationException, IllegalAcornStateException {
		return clusterLRU.getClusterByClusterUIDOrMakeProxy(clusterUID);
	}

	public int getClusterKeyByClusterUIDOrMake(ClusterUID clusterUID) throws AcornAccessVerificationException {
		return clusterLRU.getClusterKeyByClusterUIDOrMake(clusterUID);
	}

	public int getClusterKeyByClusterUIDOrMakeWithoutMutex(ClusterUID clusterUID) throws IllegalAcornStateException, AcornAccessVerificationException {
		return clusterLRU.getClusterKeyByClusterUIDOrMakeWithoutMutex(clusterUID);
	}

	public int getClusterKeyByUID(long id1, long id2) throws DatabaseException, IllegalAcornStateException {
		return clusterLRU.getClusterKeyByUIDWithoutMutex(id1, id2);
	}
	
	public <T extends ClusterI> T getClusterProxyByResourceKey(int resourceKey) throws DatabaseException, AcornAccessVerificationException, IllegalAcornStateException {
		return clusterLRU.getClusterProxyByResourceKey(resourceKey);
	}

	public ClusterUID getClusterUIDByResourceKey(int resourceKey) throws DatabaseException, AcornAccessVerificationException {
		return clusterLRU.getClusterUIDByResourceKey(resourceKey);
	}

	public ClusterUID getClusterUIDByResourceKeyWithoutMutex(int resourceKey) throws DatabaseException, IllegalAcornStateException, AcornAccessVerificationException {
		return clusterLRU.getClusterUIDByResourceKeyWithoutMutex(resourceKey);
	}

	/*
	 * Private implementation
	 * 
	 */

	private static long countFiles(Path directory) throws IOException {
		try (DirectoryStream<Path> ds = Files.newDirectoryStream(directory)) {
			int count = 0;
			for (@SuppressWarnings("unused") Path p : ds)
				++count;
			return count;
		}
	}

	// Add check to make sure if it safe to make snapshot (used with cancel which is not yet supported and may cause corrupted head.state writing)
	private AtomicBoolean safeToMakeSnapshot = new AtomicBoolean(true);
	private IllegalAcornStateException cause;
	
	public synchronized void purge(ServiceLocator locator) throws IllegalAcornStateException {
		
	    try {

	    	// Schedule writing of all data to disk
	    	refreshHeadState();
	    	// Wait for files to be written
	    	synchronizeWorkingDirectory();
	    	
	    	String currentDir = workingDirectory.getFileName().toString();
	    	Path baseline = workingDirectory.resolveSibling(currentDir + "_baseline");
	    	
	    	Files.createDirectories(baseline);
	    	
	    	for(String clusterKey : state.clusters) {
    			String[] parts1 = clusterKey.split("#");
    			String[] parts = parts1[0].split("\\.");
    			String readDirName = parts1[1];
    			if(!readDirName.equals(currentDir)) {
        			String fileName = parts[0] + "." + parts[1] + ".cluster";
        			Path from = dbFolder.resolve(readDirName).resolve(fileName);
        			Path to = baseline.resolve(fileName);
        			System.err.println("purge copies " + from + "  => " + to);
        			Files.copy(from, to, StandardCopyOption.COPY_ATTRIBUTES);
        			long first = new BigInteger(parts[0], 16).longValue();
        			long second = new BigInteger(parts[1], 16).longValue();
        			ClusterUID uuid = ClusterUID.make(first, second);
        			ClusterInfo info = clusterLRU.getWithoutMutex(uuid);
        			info.moveTo(baseline);
    			}
	    	}
	    	
    		for (String fileKey : state.files) {
    			String[] parts = fileKey.split("#");
    			String readDirName = parts[1];
    			if(!readDirName.equals(currentDir)) {
        			String fileName = parts[0] + ".extFile";
        			Path from = dbFolder.resolve(readDirName).resolve(fileName);
        			Path to = baseline.resolve(fileName);
        			System.err.println("purge copies " + from + "  => " + to);
        			Files.copy(from, to, StandardCopyOption.COPY_ATTRIBUTES);
        			FileInfo info = fileLRU.getWithoutMutex(parts[0]);
        			info.moveTo(baseline);
    			}
    		}
    		
    		for (String fileKey : state.stream) {
    			String[] parts = fileKey.split("#");
    			String readDirName = parts[1];
    			if(!readDirName.equals(currentDir)) {
    				ClusterStreamChunk chunk = streamLRU.purge(parts[0]);
        			System.err.println("purge removes " + chunk);
    			}
    		}
    		
    		// Change sets
    		for (String fileKey : state.cs) {
    			String[] parts = fileKey.split("#");
    			String readDirName = parts[1];
    			if(!readDirName.equals(currentDir)) {
    				Long revisionId = Long.parseLong(parts[0]);
    				ChangeSetInfo info = csLRU.purge(revisionId);
        			System.err.println("purge removes " + info);
    			}
//    			Path readDir = dbFolder.resolve(parts[1]);
//    			Long revisionId = Long.parseLong(parts[0]);
//    			int offset = Integer.parseInt(parts[2]);
//    			int length = Integer.parseInt(parts[3]);
//    			ChangeSetInfo info = new ChangeSetInfo(csLRU, readDir, revisionId, offset, length);
//    			csLRU.map(info);
    		}	    	
	    	
    		state.tailChangeSetId = state.headChangeSetId;
    		
	    	makeSnapshot(locator, true);
	    	
	    	Files.walk(dbFolder, 1).filter(Files::isDirectory).forEach(f -> tryPurgeDirectory(f));

	    } catch (IllegalAcornStateException e) {
	        notSafeToMakeSnapshot(e);
	        throw e;
	    } catch (IOException e) {
	        IllegalAcornStateException e1 = new IllegalAcornStateException(e);
	        notSafeToMakeSnapshot(e1);
	        throw e1;
	    } catch (AcornAccessVerificationException e) {
	        IllegalAcornStateException e1 = new IllegalAcornStateException(e);
	        notSafeToMakeSnapshot(e1);
	        throw e1;
		}
        
	}
	
	void tryPurgeDirectory(Path f) {
		
		
		System.err.println("purge deletes " + f);

		String currentDir = f.getFileName().toString();
		if(currentDir.endsWith("db"))
			return;

		if(currentDir.endsWith("_baseline"))
			currentDir = currentDir.replace("_baseline", "");

		int ordinal = Integer.parseInt(currentDir);
		if(ordinal < mainState.headDir - 1) {
			System.err.println("purge deletes " + f);
			FileUtils.deleteDir(f.toFile());
		}
		
	}

	public synchronized boolean makeSnapshot(ServiceLocator locator, boolean fullSave) throws IllegalAcornStateException {
	    try {
    	    if (!safeToMakeSnapshot.get())
    	        throw cause;
    		// Maximum autosave frequency is per 60s
    		if(!fullSave && System.nanoTime() - lastSnapshot < 10*1000000000L) {
    //		    System.err.println("lastSnapshot too early");
    		    return false;
    		}
    
    		// Cluster files are always there 
    		// Nothing has been written => no need to do anything
    		long amountOfFiles = countFiles(workingDirectory);
    		if(!fullSave && amountOfFiles == 0) {
    //		    System.err.println("amountOfFiles < 3");
    		    return false;
    		}
    
    		LOGGER.info("makeSnapshot");
    
    		// Schedule writing of all data to disk
            refreshHeadState();
    
    		// Wait for all files to be written
    		clusterLRU.shutdown();
    		fileLRU.shutdown();
    		streamLRU.shutdown();
    		csLRU.shutdown();
    		
    		// Lets check if it is still safe to make a snapshot
    		if (!safeToMakeSnapshot.get())
    		    throw cause;
    		
    		ClusterSetsSupport cssi = locator.getService(ClusterSetsSupport.class); 
    		cssi.save();

    		persistHeadState();

    		if (fullSave)
    		    mainState.save(dbFolder);
    
    		amountOfFiles = countFiles(workingDirectory);
    		
    		LOGGER.info(" -finished: amount of files is {}", amountOfFiles);
    
    		workingDirectory = dbFolder.resolve(Integer.toString(mainState.headDir));
    		if (!Files.exists(workingDirectory)) {
    		    Files.createDirectories(workingDirectory);
    		}
    
    		cssi.updateWriteDirectory(workingDirectory);
    
    		clusterLRU.setWriteDir(workingDirectory);
    		fileLRU.setWriteDir(workingDirectory);
    		streamLRU.setWriteDir(workingDirectory);
    		csLRU.setWriteDir(workingDirectory);
    
    		clusterLRU.resume();
    		fileLRU.resume();
    		streamLRU.resume();
    		csLRU.resume();
    
    		lastSnapshot = System.nanoTime();
    		
    		return true;
	    } catch (IllegalAcornStateException e) {
	        notSafeToMakeSnapshot(e);
	        throw e;
	    } catch (IOException e) {
	        IllegalAcornStateException e1 = new IllegalAcornStateException(e);
	        notSafeToMakeSnapshot(e1);
	        throw e1;
	    }
	}
	
	private void refreshHeadState() throws IOException, IllegalAcornStateException {
		state.clusters.clear();
		state.files.clear();
		state.stream.clear();
		state.cs.clear();

		clusterLRU.persist(state.clusters);
		fileLRU.persist(state.files);
		streamLRU.persist(state.stream);
		csLRU.persist(state.cs);
	}
	
	private void synchronizeWorkingDirectory() throws IOException {
		// Sync current working directory
		Files.walk(workingDirectory, 1).filter(Files::isRegularFile).forEach(FileIO::uncheckedSyncPath);
	}
	
	private void persistHeadState() throws IOException {
		synchronizeWorkingDirectory();
		state.save(workingDirectory);
		mainState.headDir++;
	}

	
//	public void save() throws IOException {
//
//		refreshHeadState();
//		
//		clusterLRU.shutdown();
//		fileLRU.shutdown();
//		streamLRU.shutdown();
//		csLRU.shutdown();
//
//		persistHeadState();
//
//		mainState.save(getBaseDirectory());

//		try {
//			ThreadLogVisualizer visualizer = new ThreadLogVisualizer();
//			visualizer.read(new DataInputStream(new FileInputStream(
//					ThreadLogger.LOG_FILE)));
//			visualizer.visualize3(new PrintStream(ThreadLogger.LOG_FILE
//					+ ".svg"));
//		} catch (FileNotFoundException e) {
//			// TODO Auto-generated catch block
//			e.printStackTrace();
//		}

		// System.err.println("-- load statistics --");
		// for(Pair<ClusterUID, Integer> entry :
		// CollectionUtils.valueSortedEntries(histogram)) {
		// System.err.println(" " + entry.second + " " + entry.first);
		// }

//	}
	
	private void acquireAll() throws IllegalAcornStateException {
		clusterLRU.acquireMutex();
		fileLRU.acquireMutex();
		streamLRU.acquireMutex();
		csLRU.acquireMutex();
	}
	
	private void releaseAll() {
		csLRU.releaseMutex();
		streamLRU.releaseMutex();
		fileLRU.releaseMutex();
		clusterLRU.releaseMutex();
	}

	private AtomicBoolean rollback = new AtomicBoolean(false);
	
	boolean rolledback() {
	    return rollback.get();
	}
	
	public void load() throws IOException {

		// Main state
		mainState = MainState.load(dbFolder, () -> rollback.set(true));

		lastSessionDirectory = dbFolder.resolve(Integer.toString(mainState.headDir - 1));
		
		// Head State
		try {
            state = HeadState.load(lastSessionDirectory);
        } catch (InvalidHeadStateException e) {
            // For backwards compatibility only!
            Throwable cause = e.getCause();
            if (cause instanceof Throwable) {
                try {
                    org.simantics.db.javacore.HeadState oldState = org.simantics.db.javacore.HeadState.load(lastSessionDirectory);
                    
                    HeadState newState = new HeadState();
                    newState.clusters = oldState.clusters;
                    newState.cs = oldState.cs;
                    newState.files = oldState.files;
                    newState.stream = oldState.stream;
                    newState.headChangeSetId = oldState.headChangeSetId;
                    newState.reservedIds = oldState.reservedIds;
                    newState.transactionId = oldState.transactionId;
                    state = newState;
                } catch (InvalidHeadStateException e1) {
                    throw new IOException("Could not load HeadState due to corruption", e1);
                }
            } else {
                // This should never happen as MainState.load() checks the integrity
                // of head.state files and rolls back in cases of corruption until a
                // consistent state is found (could be case 0 - initial db state)
                // IF this does happen something is completely wrong
                throw new IOException("Could not load HeadState due to corruption", e);
            }
        }
		try {
    		workingDirectory = dbFolder.resolve(Integer.toString(mainState.headDir));
    		Files.createDirectories(workingDirectory);
    
    		csLRU = new LRU<Long, ChangeSetInfo>(this, "Change Set", workingDirectory);
    		streamLRU = new LRU<String, ClusterStreamChunk>(this, "Cluster Stream", workingDirectory);
    		clusterLRU = new ClusterLRU(this, "Cluster", workingDirectory);
    		fileLRU = new LRU<String, FileInfo>(this, "External Value", workingDirectory);
    
    		acquireAll();
    		
    		// Clusters
    		for (String clusterKey : state.clusters) {
    			String[] parts1 = clusterKey.split("#");
    			String[] parts = parts1[0].split("\\.");
    			long first = new BigInteger(parts[0], 16).longValue();
    			long second = new BigInteger(parts[1], 16).longValue();
    			ClusterUID uuid = ClusterUID.make(first, second);
    			Path readDir = dbFolder.resolve(parts1[1]);
    			int offset = Integer.parseInt(parts1[2]);
    			int length = Integer.parseInt(parts1[3]);
    			clusterLRU.map(new ClusterInfo(this, clusterLRU, readDir, uuid, offset, length));
    		}
    		// Files
    		for (String fileKey : state.files) {
    //			System.err.println("loadFile: " + fileKey);
    			String[] parts = fileKey.split("#");
    			Path readDir = dbFolder.resolve(parts[1]);
    			int offset = Integer.parseInt(parts[2]);
    			int length = Integer.parseInt(parts[3]);
    			FileInfo info = new FileInfo(fileLRU, readDir, parts[0], offset, length);
    			fileLRU.map(info);
    		}
    		// Update chunks
    		for (String fileKey : state.stream) {
    //			System.err.println("loadStream: " + fileKey);
    			String[] parts = fileKey.split("#");
    			Path readDir = dbFolder.resolve(parts[1]);
    			int offset = Integer.parseInt(parts[2]);
    			int length = Integer.parseInt(parts[3]);
    			ClusterStreamChunk info = new ClusterStreamChunk(this,
    					streamLRU, readDir, parts[0], offset, length);
    			streamLRU.map(info);
    		}
    		// Change sets
    		for (String fileKey : state.cs) {
    			String[] parts = fileKey.split("#");
    			Path readDir = dbFolder.resolve(parts[1]);
    			Long revisionId = Long.parseLong(parts[0]);
    			int offset = Integer.parseInt(parts[2]);
    			int length = Integer.parseInt(parts[3]);
    			ChangeSetInfo info = new ChangeSetInfo(csLRU, readDir, revisionId, offset, length);
    			csLRU.map(info);
    		}
    		
    		releaseAll();
		} catch (IllegalAcornStateException | AcornAccessVerificationException e) {
		    // ROLLBACK ONE DIR UNTIL WE ARE FINE!
		    throw new IOException(e);
		}
	}

	public <T> T clone(ClusterUID uid, ClusterCreator creator) throws DatabaseException, AcornAccessVerificationException, IllegalAcornStateException, IOException {
		
		clusterLRU.ensureUpdates(uid);
		
		ClusterInfo info = clusterLRU.getWithoutMutex(uid);
		return info.clone(uid, creator);
	}

	//private int loadCounter = 0;

	public static void startLog(String msg) {
		tasks.put(msg, ThreadLogger.getInstance().begin(msg));
	}

	public static void endLog(String msg) {
		ITask task = tasks.get(msg);
		if (task != null)
			task.finish();
	}

	static Map<String, ITask> tasks = new HashMap<String, ITask>();

	public void update(ClusterUID uid, ClusterImpl clu) throws AcornAccessVerificationException, IllegalAcornStateException {
		ClusterInfo info = clusterLRU.getWithoutMutex(uid);
		info.acquireMutex();
		try {
			info.update(clu);
		} finally {
			info.releaseMutex();
		}
	}

	public long getClusterIdOrCreate(ClusterUID clusterUID) {
		return 1;
	}

	public int getResourceKey(ClusterUID uid, int index) throws AcornAccessVerificationException {
		return clusterLRU.getResourceKey(uid, index);
	}

	public int getResourceKeyWitoutMutex(ClusterUID uid, int index) throws IllegalAcornStateException {
		return clusterLRU.getResourceKeyWithoutMutex(uid, index);
	}

	public ClusterIds getClusterIds() throws IllegalAcornStateException {
		clusterLRU.acquireMutex();

		try {
			Collection<ClusterInfo> infos = clusterLRU.values();
			final int status = infos.size();
			final long[] firsts = new long[status];
			final long[] seconds = new long[status];

			int index = 0;
			for (ClusterInfo info : infos) {
				firsts[index] = 0;
				seconds[index] = info.getKey().second;
				index++;
			}

			return new ClusterIds() {

				@Override
				public int getStatus() {
					return status;
				}

				@Override
				public long[] getFirst() {
					return firsts;
				}

				@Override
				public long[] getSecond() {
					return seconds;
				}

			};

		} catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			clusterLRU.releaseMutex();
		}
	}

	public void addIntoCurrentChangeSet(String ccs) throws IllegalAcornStateException {
		csLRU.acquireMutex();

		try {
			currentChanges.add(ccs);
		} catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			csLRU.releaseMutex();
		}
	}

	public void commitChangeSet(long changeSetId, byte[] data) throws IllegalAcornStateException {
		csLRU.acquireMutex();
		try {
			ArrayList<String> csids = new ArrayList<String>(currentChanges);
			currentChanges = new ArrayList<String>();
			new ChangeSetInfo(csLRU, changeSetId, data, csids);
		} catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			csLRU.releaseMutex();
		}
	}

	public byte[] getMetadata(long changeSetId) throws AcornAccessVerificationException, IllegalAcornStateException {
		
		ChangeSetInfo info = csLRU.getWithoutMutex(changeSetId);
		if (info == null) return null;
        info.acquireMutex();
        try {
            return info.getMetadataBytes();
        } catch (IllegalAcornStateException | AcornAccessVerificationException e) {
            throw e;
        } catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			info.releaseMutex();
		}
	}

	public byte[] getResourceFile(final byte[] clusterUID, final int resourceIndex) throws AcornAccessVerificationException, IllegalAcornStateException {

		ClusterUID uid = ClusterUID.make(clusterUID, 0);
		String key = uid.toString() + "_" + resourceIndex;
		FileInfo info = fileLRU.getWithoutMutex(key);
		if(info == null) return null;
		info.acquireMutex();
		try {
			return info.getResourceFile();
		} catch (IllegalAcornStateException | AcornAccessVerificationException e) {
		    throw e;
		} catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			info.releaseMutex();
		}
	}

	public ResourceSegment getResourceSegment(final byte[] clusterUID, final int resourceIndex, final long segmentOffset, short segmentSize) throws AcornAccessVerificationException, IllegalAcornStateException {
		ClusterUID uid = ClusterUID.make(clusterUID, 0);

		String key = uid.toString() + "_" + resourceIndex;
		FileInfo info = fileLRU.getWithoutMutex(key);
		if(info == null) return null;
		info.acquireMutex();
		try {
			return info.getResourceSegment(clusterUID, resourceIndex, segmentOffset, segmentSize);
		} catch (Throwable t) {
			throw new IllegalAcornStateException(t);
		} finally {
			info.releaseMutex();
		}
	}

	public void modiFileEx(ClusterUID uid, int resourceKey, long offset, long size, byte[] bytes, long pos, ClusterSupport support) throws IllegalAcornStateException {
		try {
			String key = uid.toString() + "_" + ClusterTraits.getResourceIndexFromResourceKey(resourceKey);

			FileInfo info = null;
			fileLRU.acquireMutex();
			try {
				info = fileLRU.get(key);
				if (info == null) {
					info = new FileInfo(fileLRU, key, (int) (offset + size));
				}
			} catch (Throwable t) {
				throw new IllegalAcornStateException(t);
			} finally {
				fileLRU.releaseMutex();
			}
			
			info.acquireMutex();
			try {
				info.updateData(bytes, offset, pos, size);
			} catch (Throwable t) {
				throw new IllegalAcornStateException(t);
			} finally {
				info.releaseMutex();
			}
		} catch (DatabaseException e) {
			e.printStackTrace();
		}
	}

    public void shutdown() {
        clusterLRU.shutdown();
        fileLRU.shutdown();
        streamLRU.shutdown();
        csLRU.shutdown();
    }

    public void notSafeToMakeSnapshot(IllegalAcornStateException t) {
        this.safeToMakeSnapshot.compareAndSet(true, false);
        this.cause = t;
    }

    public long getTailChangeSetId() {
    	return state.tailChangeSetId;
    }
    
}